The oral cavity is colonized by a large number of viridans streptococci, including primarily soft-tissue colonizers like Streptococcus salivarius and S. mitis, and predominantly hard-tissue (teeth) colonizers like S. mutans and S. gordonii. Among teeth colonizers, S. mutans is considered the primary etiologic agent of dental caries, an infectious disease that affects 60-90% of the population worldwide (Surgeon General, Promoting Oral Health: Interventions for Preventing Dental Caries, Oral and Pharyngeal Cancers, and Sports-Related Craniofacial Injuries, 50:1-13 (2001)). Strains of S. mutans can be grouped into four serotypes (c, e, f and k) based on the composition and structure of the rhamnose glucose polysaccharide (RGP) associated with the cell wall. Epidemiological studies revealed that serotype c is the most common serotype isolated from dental plaque, being found in nearly 80% of the S. mutans positive samples. Serotypes e and f are found in about 20% and 2% of the patients, respectively (Hirasawa et al., “A New Selective Medium for Streptococcus mutans and the Distribution of S. mutans and S. sobrinus and their Serotypes in Dental Plaque,” Caries Res 37:212-7 (2003); Nakano et al., “Demonstration of Streptococcus mutans with a Cell Wall Polysaccharide Specific to a New Serotype, k, in the Human Oral Cavity,” J Clin Microbiol 42:198-202 (2004); Shibata et al., “Analysis of Loci Required for Determination of Serotype Antigenicity in Streptococcus mutans and Its Clinical Utilization,” J Clin Microbiol 41:4107-12 (2003)). Strains belonging to serotype k are the most infrequent, having thus far been isolated only in subjects from Japan, Thailand and Finland (Lapirattanakul et al., “Detection of Serotype k Streptococcus mutans in Thai Subjects,” Oral Microbiol Immunol 24:431-3 (2009); Nakano et al., “Detection of Novel Serotype k Streptococcus mutans in Infective Endocarditis Patients,” J Med Microbiol 56:1413-5 (2007); Nakano et al., “Serotype Classification of Streptococcus mutans and Its Detection Outside the Oral Cavity,” Future Microbiol 4:891-902 (2009)).
In addition to colonizing the teeth in significant numbers, it is not unusual for S. mutans to gain access to the bloodstream during dental procedures (Drangsholt, “A New Causal Model of Dental Diseases Associated with Endocarditis,” Ann Periodontol 3:184-96 (1998); Hill et al., “Evolving Trends in Infective Endocarditis,” Clin Microbiol Infect 12:5-12 (2006); Kilian M., Systemic Disease: Manifestations of Oral Bacteria, in Dental Microbiology 832-838 (J. R. McGee, S. M. Michalek, and G. H. Cassell eds., 1982)). If a sufficient number of cells enter the circulation, transient bacteremia followed by adhesion to endothelial cells may lead to infective endocarditis (IE) (Kilian M., Systemic Disease Manifestations of Oral Bacteria, in Dental Microbiology 832-838 (J. R. McGee, S. M. Michalek, and G. H. Cassell eds., 1982); Moreillon et al., “Infective Endocarditis,” Lancet 363:139-49 (2004)), particularly in persons with pre-disposing cardiac conditions. In addition to IE, a significant association between dental infections and the occurrence of coronary atherosclerosis has been demonstrated (Meurman et al., “Oral Health, Atherosclerosis, and Cardiovascular Disease,” Crit. Rev Oral Biol Med 15:403-13 (2004)). More specifically, oral streptococci and the periodontal pathogen Porphyromonas gingivalis have been associated with artherosclerotic/atheromatous plaques (Douglas et al., “Identity of Viridans Streptococci Isolated from Cases of Infective Endocarditis,” J Med Microbiol 39:179-82 (1993); Haraszthy et al., “Identification of Periodontal Pathogens in Atheromatous Plaques,” J Periodontol 71:1554-60 (2000); Li et al., “Porphyromonas gingivalis Infection Accelerates the Progression of Atherosclerosis in a Heterozygous Apolipoprotein E-deficient Murine Model,” Circulation 105:861-7 (2002); Meurman et al., “Oral Health, Atherosclerosis, and Cardiovascular Disease,” Crit. Rev Oral Biol Med 15:403-13 (2004); Van der Meer et al., “Efficacy of Antibiotic Prophylaxis for Prevention of Native-valve Endocarditis,” Lancet 339:135-9 (1992)). Studies by Nakano and co-workers (Nakano et al., “Detection of Cariogenic Streptococcus mutans in Extirpated Heart Valve and Atheromatous Plaque Specimens,” J Clin Microbiol 44:3313-7 (2006); Nakano et al., “Serotype Classification of Streptococcus mutans and Its Detection Outside the Oral Cavity,” Future Microbiol 4:891-902 (2009); Nemoto et al., “Molecular Characterization of Streptococcus mutans Strains Isolated from the Heart Valve of an Infective Endocarditis Patient,” J Med Microbiol 57:891-5 (2008)) reported that among bacterial species, S. mutans DNA was the most frequently detected in diseased heart valve tissues and atheromatous plaque, suggesting that S. mutans may play an important and underestimated role in the onset of cardiovascular diseases (CVD) (Nakano et al., “Detection of Cariogenic Streptococcus mutans in Extirpated Heart Valve and Atheromatous Plaque Specimens,” J Clin Microbiol 44:3313-7 (2006)). However, detection of bacteria in atheromas has been based on amplification of S. mutans DNA and not from isolation of live bacteria. Recently, it has been demonstrated that two S. mutans strains, B14 and OMZ175, belonging to serotypes e and f, respectively, invade and persist in the cytoplasm of cultured human coronary artery endothelial cells (HCAEC), revealing a possible new facet of the pathogenic potential of S. mutans and a mechanistic linkage of S. mutans to CVD (Nakano et al., “Detection of Cariogenic Streptococcus mutans in Extirpated Heart Valve and Atheromatous Plaque Specimens,” J Clin Microbiol 44:3313-7 (2006)). However, evidence of cell invasion in vivo is lacking.
It would be desirable, therefore, to determine whether cell invasion occurs during IE and other cardiovascular disease, and, if so, whether one or more proteins expressed by invasion-capable strains can serve as a marker for the invasive phenotype. Some S. mutans surface structures, such as the P1 protein, also known as antigen I/II or SpaP, the wall anchored protein A (WapA), the biofilm regulatory protein A (BrpA), the autolysin AtlA, the glucosyltransferases (GtfB, GtfC, and GtfD), and the serotype-specific rhamnose-glucose polysaccharide (RGP) have been implicated in the pathogenesis of IE by promoting adherence to endothelial tissues and triggering inflammatory responses (Shun et al., “Glucosyltransferases of Viridans Streptococci are Modulins of Interleukin-6 Induction in Infective Endocarditis,” Infect Immun 73:3261-70 (2005); Engels-Deutsch, “Insertional Inactivation of pac and rmlB Genes Reduces the Release of Tumor Necrosis Factor alpha, Interleukin-6, and Interleukin-8 Induced by Streptococcus mutans in Monocytic, Dental Pulp, and Periodontal Ligament Cells,” Infect Immun 71:5169-77 (2003); Vernier-Georgenthum et al., “Protein I/II of Oral Viridans Streptococci Increases Expression of Adhesion Molecules on Endothelial Cells and Promotes Transendothelial Migration of Neutrophils in vitro,” Cell Immunol 187:145-50 (1998)). More recently, a new surface protein with collagen and laminin binding activity, Cnm, which has an uneven distribution among the different serotypes of S. mutans, was identified (Nomura et al., “Molecular and Clinical Analyses of the Gene Encoding the Collagen-Binding Adhesin of Streptococcus mutans,” J Med Microbiol 58:469-75 (2009); Sato et al., “Streptococcus mutans Strains Harboring Collagen-Binding Adhesin,” J Dent Res 83:534-9 (2004); Sato et al., “Application of in vitro Mutagenesis to Identify the Gene Responsible for Cold Agglutination Phenotype of Streptococcus mutans,” Microbiol Immunol 48:449-56 (2004)).
The present invention is directed to overcoming these and other deficiencies in the art.